Wednesday, October 26, 2011

Harlequin Ladybird (Harmonia axyridis var. succinea) adult at site of establishment near Cork city

Our recent record of the Harlequin Ladybird (Harmonia axyridis) prompted me to reexamine some older pictures of Coccinellidae beetles, to see if any other of the morphs had inadvertently been seen. Lo and behold, buried among the pictures of moths, flowers and wading birds, there was an example of H. axyridis var. succinea. However, this was just one picture among about 25 taken. The rest showed no more adults, but, worryingly, did show many, many pupae as well as larvae. These pictures taken on the 19th of October, 2010 show the first evidence of establishment of H. axyridis in Ireland.

Harlequin Ladybird (Harmonia axyridis) pupa at site of establishment near Cork city

The site of establishment is a collection of Griselinia littoralis bushes that border a footpath and that is backed by a small stream on a previously heavily industrialised area about 2 km from Cork city centre. The area is quite near the river Lee, Cork city's main river, and also near Tivoli Dock, a major container port that may be the site of entrance for H. axtridis. Examination of the site last week, just over a year after the first sighting, showed H. axyridis pupae still present on the same G. littoralis bushes, showing that it survived the unprecedently harsh weather last winter, something that has been observed in other countries such as Belgium (1). This is not the only site, with another being reported from Co. Carlow in July of this year. Establishment of H. axridis in Ireland is worrying, as they have had adverse effects on other Coccinellidae species where introduced in North America, reducing numbers by up to 20 times in some cases (2). They have also been seen to cause damage through feeding to soft fruits (grapes) and pears.

Harlequin Ladybird (Harmonia axyridis) larva at site of establishment near Cork city

Wednesday, October 19, 2011

Leiobunum rotundum, feeding. Note the missing second leg on the animals left side. This is an example of autopasy, a defensive strategy involving losing an appendage along a preformed brake plane in response to stress such as a predator.

Everybody knows them, but few know much about them: Daddy Long Legs. Because of this lack of knowledge, much of what is known is superstition and folklore. Even the very name we give them, 'Daddy Long Legs', suggests a monstrous, lurking menace rather than the fascinating and ancient creatures that they are.
Daddy-Long-Legs (or Harvestmen) are arachnids of the order Opiliones and with over 5000 species described they are the third largest group of arachnids after the Acari (mites and ticks) and Aranae (spiders) (1). Their body has two basic regions; a prosoma (or cephalothorax) which carries all the appendages and eyes, and a limbless opisthosoma (or abdomen) which has the spiracels and genital opening. Although they resemble spiders, the two body regions are not clearly defined and they thus lack the constriction or waist that can be seen in spiders. Opiliones also lack spinning organs and so do not spin webs. They are in fact much more closely related to scorpions and pseudoscorpions (2) and are among the oldest of arachnids, with fossil records showing little morphological change in the group in 400 million years (1). They possess many characteristics that are unique to their group. These include the presence of paired trachae, the presence of a penis or spermatopositor organ in males and an ovipoistor in females and scent glands that are present on the prosoma (3). These glands release chemicals during defensive behaviour that can repel other arthropods (4). Other than these chemicals, opiliones do not produce venom and the commonly held belief that they are poisonous is untrue.
They are found on every continent, bar Antarctica, in moist to wet habitats and are excellent indicators of undisturbed environments where they feed on arthropods, snails and worms. These they ingest in particles, unlike many arachnids which need to liquify their food, and also may eat vegetable matter (2). Most species in the Northern Hemisphere overwinter as eggs, hatching in the spring. Maternal care is common in opiliones, as it is in many other arachnid groups, but uniquely so is paternal care. Adults reach maturity in the Autumn, which has lent them one of their common names, Harvestmen. Many species are very tolerant of other individuals, again unlike other arachnid groups, and often large aggregations of adults and subadults can be seen near water sources.
One of the most conspicuous of the 18 species of opiliones present in Ireland (15 native, 3 introduced and naturalised) (5) is the longlegged Leiobunum rotundum. Preferring open spaces, L. rotundum feeds on a variety of invertebrate prey as well as soft fruits (6). The individual pictured is mising one of its legs and thus shows an example of autopasy (also called autotomy). This is a situation where an outside agent is responsible for the severance of an appendage at a preformed breakage plane (e.g., the loss of limb to a predator who has seized it) (7). The limb will not grow back.

Monday, October 17, 2011

Ireland scored a little bit of a coup when Irish Spurge was given the scientific name Euphorbia hyberna. A spurge from Ireland, is the (very) rough translation, even though it is also found extensively in the south-western Mediterranean region and northern Portugal (1). Indeed its distribution in Ireland is limited to the south-west of the country, in Co. Kerry and west Co. Cork. It is to be found in damp, shaded areas, particularly wooded slopes where its upright stems bear striking yellow flowers that lack sepals or petals (2) and that were unfortunately gone from the plant pictured here. Due to its distribution in Iberia and the west of Ireland, it is frequently quoted as one of the 'Lusitana Flora' common to both areas, but lacking in the flora of Ireland's nearest neighbour, Britain. However this assertion is not true: E. hybernia is present in the flora of West Cornwall, North Devon and South Somerset, being extremely local in all three areas (3).

In the race to be the top of the heap in biological terms, organisms can follow two paths. They can take their time about it all, growing nice and big and strong, but missing out every time a potential mate comes by and they are not developed enough to take advantage of the situation. Or they can rush into things, becoming sexually mature quickly but growing to be small in size, and possibly unattractive to potential mates. What makes this choice all the more difficult is the prevalent environmental conditions that can, and often do, hinder the organsisms development. Availability of resources, threats from predators and the vagaries of the seasons mean that the chosen path is soon skewed. This has been elegantly demonstrated in a series of studies on the Emerald Damselfly, Lestes sponsa (1). This attractive, bottle-green odonate overwinters in the egg stage, has a brief larval period in spring, then emerges and reproduces in late June, the latest Irish damselfly to do so. It is common and widespread through out Ireland, commonly found near small lakes and acid ponds. L. sponsa individuals were measured for foraging activity, development rate and mass at emergence when exposed to the presence/absence of predators and the perceived onset of winter, and the abundance/scarcity of food and, again, the perceived onset of winter. In the presence of predators, all three perameters measured were reduced, while individuals under time constraints showed increased foraging and development, but decreased mass at emergence. Larvae that had an abundance of food showed high levels of all three parameters, while those that had time constraints in high levels of food showed lower mass at emergence, as was to be expected. What was not expected, however, was larvae at low food levels under time constraints showed very slow development and that largest mass at emergence. This is thought to be a result of this last group delaying emergence until the following season. Such life history plasticity is a feature of the life of L. sponsa.

One of the most imminent threats to native Irish species by invasives is the one the Harlequin Ladybird (Harmonia axyridis) poses to Irish native ladybirds. H. axyridis is larger and more aggressive than native Irish ladybird species and is thus able to out-compete them in hunting their preferred food of aphids. They also can have up to four generations per year, compared to the just one for native ladybird species and display less susceptibility to common diseases and parasites (1). Allied to this, H. axyridis also targets many non-aphid insect species, such as lepidopteran larvae and, most worryingly, ladybird larvae (2).

Harlequin Ladybird, Harmonia axyridis f. spectabilis

H. axyridis is native to Asia, specifically China, Japan, Korea, Mongolia and Siberia (1). Its voracious appetite for aphids marked it out as a seemingly effective biolocontrol agent and was introduced as such into the US in 1916. Establishment took some time but H. axyridis was recorded as such in 1988 and is now considered a pest there. Other than its effect on native ladybird populations, its tendency to overwinter in nooks and crannies in houses in quite large numbers make it a nuisance and may cause allergic reactions in inhabitants. Despite such problems, H. axyridis was inexplicably marketed as a biocontrol agent in mainland Europe in the 1990s. Commercial field releases first occurred in 1995 in France and was subsequently introduced as such in Belgium, Germany, Greece, Italy, the Netherlands, Spain, Portugal and Switzerland. H. axyridis has since spread to Austria, Luxembourg, Demark, Norway, Sweden and Great Britain, where it was first recorded in 2004 (3). The first Irish record for H. axyridis was in 2007 in Co. Down, with the first record for the Republic being in 2010 in Co. Wicklow (4). Another individual was recorded in 2010 in Cork City in November entering a house where individuals are wont to overwinter.
The individual pictured here was sighted entering a dwelling in the suburbs of Cork City on the 12th of October. Specifically, it was H. axyridis f. spectabilis that was sighted. This is the same variety that was seen in both records in 2010. Two other varieties are present throughout Europe, f. succinea and f. conspicua. H. axyridis is distinguished from other ladybird species by being noticibly larger, having red legs, being more domed than other species and may have a distinctive 'M' or 'W' mark on its pronotum (4).

Monday, October 10, 2011

I recently saw a Pipistrelle bat fly past my window, its erratic flying pattern indicating it was feeding. Now I don't claim to have excellent eyesight, butI knew it a Pipistrelle as I know there is a roost nearby. Beyond this however, I could not say what species it was. Ireland has three species of Pipistrelle: Nathusius’ Pipistrelle (Pipistrellus nathusii), the Common Pipistrelle (P. pipistrellus) and the Soprano Pipistrelle (P. pygmaeus). The only confirmed breeding colony for P. nathusii in Ireland was recorded in 1997 near Lough Neagh and while there has been recordings in other counties, no records exist for the bat as far south as where I live (1). Its therefore extremely unlikely that is was P. nathusii that I saw. So that leaves P. pipistrellus or P. pygmaeus. However if I had spotted this bat pre-1999, I would have been sure that it was P. pipistrellus. Prior to this, P. pygmaeus was not recognised as a species in its own right. The two species are morphologically identical, measuring about 4 cm long with a 20 cm wingspan. Their difference lies in the frequency used by both bats during echo location (2). P. pipistrellus uses a call of 45 kHz, with P. pygmaeus using one of 55kHz. While differences were noted within the P. pipistrellus species as early as 1865 (2), it wasn't until the 1980s that the use of bat detectors revealed differences in the echo locating frequency of the two species. Further investigation showed that the two species occurred in close association however they did not share roosts. Conclusive support for the two-species theory was provided in differences in the cytochrome b genes.

Friday, October 7, 2011

Gunnera are big. Very big. Well, not all of them: Gunnera herteri stands only 6 cm tall (1). But the big ones are very big. They're old too, with the fossil record showing they have been in existence for at least 95 million years. It is their size, however, that is most obviously impressive. G. mantica has a leaf diameter of 3 m (1). Its not alone in this, with many other of the c. 50 species of this monogeneric family towering, in some cases 6 meters, over any other vegetation.

Gunnera tinctoria

This height has posed a problem in Ireland where the species G. tinctoria was was introduced from its native Chile some time in the past 100 years, probably as a ornamental. While not as big as enormous as some of the Gunnera giants, it still clocks in at an impressive 2 meters tall with leaves 2 meters in diameter. It tends to grow in dense colonies that out-compete and displace native vegetation. It was first recorded wild here by the renowned Irish botanist Robert Lloyd Praeger in 1939 on Achill Island, Co. Mayo and it is here today that the plant colloquially called 'Giant Rhubarb' shows the extent of its dominance (2). Large tracts of the island are now almost entirely covered with G. tinctoria. As such, it is considered an invasive in the west of Ireland where it has colonised many habitats such as grassland, waterways, roadside verges, bogs, heaths and coastal cliffs (3). While its sparse distribution throughout the rest of the country may be reflective of the different climatic conditions there, it may also may just be evidence of the beginning of its invasion.

Gunnera tinctoria leaf

While the size of G. tinctoria accounts for its adverse effect on other plants, it is its methods of reproduction that account for its invasive nature. As a perennial rhizomatous plant, it can spread easily from year to year once established. It also produced many seeds which may be carried to new sites by birds feeding on them (3). Ireland's wet climate also assists these damp loving plants, which accounts for their status as an invasive in similarly inclement New Zealand. The rhizomes mean mechanical removal may not always be effective, so herbicides such as Round-Up are a valuable tool in controlling the plant.

Gunnera tinctoria flowering parts

Other than their height, Gunner species also possess a distinct adaptation that singles them out from all other flowering plants. They form symbiotic relationships with Nostoc cyanobacteria (4). The cyanobacteria are uniquely harboured internally by the plants which surround the Nostoc filaments with membranes where they fix nitrogen for the plant. Entry is made via specialised glands on the Gunnera stems. Interestingly it has been shown that G. manicata grown on substrate with sufficient nitrogen did not develop these glands (4).

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